I want few users to charge time in OTL but it should not get accounted at costing

Summary:

I have few users who would like to use OTL for time charging but it it should not be accounted in costing side? How do i control at project level? Can i create task which is non billable?

Content (please ensure you mask any confidential information):

Task as non billable

Version (include the version you are using, if applicable):

25B

Code Snippet (add any code snippets that support your topic, if applicable):